Platinum-alumina-ceria hydroforming catalyst and process



Unite PLATINUM-ALUMINA-CERIA HYDROFORMING CATALYST AND PROCESS No Drawing. Filed Jan. 19, 1959, Ser. No.187,348 6 Claims. or. 208-138) This application relates to novel platinum-group metal catalysts and to a method employing said catalysts for hydroforming naphtha fractions to produce high octane number motor fuels. More particularly this invention pertains to novel platinum-group metal catalysts, preferably platinum per se upon alumina supports which are stabilized by the incorporation of relatively small amounts of a stabilizer substance.

Platinum catalysts are well known and widely used for the treatment of hydrocarbon fractions boiling in the motor gasoline range under hydroforming reaction conditions in order to produce high octane number, clean burning gasolines. In view of the high costs of platinum-alumina hydroforming catalysts it is necessary, to compete economically, that such catalysts possess high activity, so that large amounts of naphtha feed can be charged to a given conversion unit per unit of time These catalysts must, in addition to high activity, also possess good selectivity or be able to produce high yields of high octane number products with small production of normally gaseous or solid carbonaceous by-products. It is also'necessary that these catalysts possess good stability so that they retain good activity and selectivity characteristics during prolonged periods of operation and, when necessary, that they be capable of regeneration and/or reactivation by burning carbonaceous deposits therefrom and treating the essentially carbon-free catalyst with oxygen-containing and/or chlorine-containing gas. The latter property is of the utmost importance, since it is only by going to relatively drastic reaction conditions that desired octane number products are produced, and under these reaction conditions, regeneration and reactivation of the catalyst is required at very frequent intervals.

It has been previously proposed to add activators or promoters to hydroforming catalysts consisting of platinum dispersed or.supported upon a carrier. U.S. Patent 2,814,599, for example, proposes to add a compound of agroup III metal having an atomic number of at least 21 and not more than 89 as an activating agent. Within this group of compounds it has been found that While gallium effects a substantial activation of a platinum alumina catalyst, yttrium actually deactivates such catalysts.

It has now been'found that the stability with respect to platinum crystallite formation of platinum-alumina reforming catalysts can be improved remarkably by impregnation of ceria upon the surface of the platinum alumina catalyst. It has been found that while the ceria tends to lower the initial activity of the fresh catalyst, the presence of small amounts of ceria does aremarkably good job of reducing the rate of deactivation of platinumalumina when'the ceria is impregnated upon the surface ofthe carrier. It is known that active platinum hydroforming catalysts are characterized by having the platinum widely distributed (high platinum surface area) while the deactivated catalyst has low platinum surface area with the platinum in the form of large crystallites Ftent crystallite growth is attributable to the fact that the migration temperature for platinum upon alumina supports is about 900-F. (lower than normal hydroforming temperature). It is believed that by impregnating ceria upon the surface of a platinum on alumina catalyst that the migration temperature of the platinum is raised very substantially thereby improving the stability of the catalyst by inhibiting platinum crystal growth.

The catalysts which are improved in stability in accordance with the present; invention are those consisting essentially of a platinum group metal, preferably platinum 'per se, distributed upon an adsorptive aluminacontaining support or carrier. Preferably, the support material is a high purity alumina in the eta crystal form derived by hydrolyzing aluminum alcoholate, drying and calcining in known manner. The platinum-alumina catalyst can be prepared by compositinga platinum group metal compound with adsorptive alumina, i.e., after the alumina hydrate has been calcined to fix or establish the structure of the adsorptive alumina in any known manner.

The simplest method is merely to impregnate the calcined alumina with a suitable solution, for example, a solution of chloroplatinic acid. More uniform distribution of the platinum on the alumina can be achieved by suspending the alumina in an excess of deionized water and slowly adding the solution of the platinum compound to the dilute slurry with stirring, or the dry alumina may be mixed directly with the solution of the platinum compound. The impregnated alumina is separated from any excess liquid, dried at about 250 F. and calcined at about 1000 to 1200" F. for from about 1 to 24 hours.

The catalysts contain the platinum group metal in the usual amounts, i.e., about 0.01 to 5% by weight, preferably about 0.1 to 1.0 wt. percent in the case of platinum per se. p

The ceria is composited with the catalyst by wet impregnation simultaneously with or subsequent. to the impregnation with the platinum group metal compound. Suitable salts for the preparation of an impregnation solution are cerous acetate, chloride or nitrate. Any

' compound of cerium can be used which will readily decompose to ceria upon calcination, and accordingly the chloride and the nitrate are preferred. The amount of cerium compound added should be suflicient to provide from about 0.05 to about 5.0 wt. percent, preferably 0.1

to 1.0 wt. percent of Ce O in the catalyst composition;

After completion of the impregnation, the catalyst is dried and calcined at 1000-1200" F. for 1 to 24 hours.

Ordinarily it is preferred to incorporate the cerium com-' pound in the catalyst at the same time that the platinum compound is added in order to avoid an extra drying and calcination step. The catalyst is desirably given a short treatment with hydrogen before use in the reforming of hydrocarbon fractions. 'This is conveniently effected by bringing the catalyst up to conversion conditions of temperature and pressure in the presence of a hydrogencontaining gas.

The catalysts prepared in accordance with the present invention are particularly adapted for reforming hydrocarbon fractions boiling in the naphtha boiling range, or from about -200 F. to about 400 F. The reforming can be effected in fixed, moving or fluidized beds as known in the art. In the fluidized solids operation, it is preferred to use a dilute catalyst prepared by first making a catalyst concentrate by compositing about 0.2. to' 1.0 wt. percent platinum and 0.5 to 5.0 wt. percent ceria with an adsorptive alumina and then mixing one part of this catalyst concentrate with several parts, for ex-l ample, about nine parts of unplatinized calcined alumina.

Reforming of naphtha feeds is effected by contacting a feed naphtha in the vapor phase with the catalysts of this invention at temperatures between about 800 and 1000 F., pressures of from 100 to 1000 p.s.i.g. at hourly space velocities of about 0.5 to 10 and in the presence of from about 2,000 to 10,000 s.c.f./b. of hydrogen or hydrogen-rich recycle gas. It is preferred to utilize these catalysts at pressures below about 450 p.s.i.g. in order to obtain the maximum benefit of their greater stability.

The following examples are illustrative of the present invention.

EXAMPLE 1 Aluminum amylate solution was hydrolyzed in the presence of acetic acid as per U.S. Patent 2,656,321 and the resultant alumina hydrosol formed upon heating was spray dried to produce alcoholate alumina gel particles. The latter were calcined for 6 hours at 1100 F.

Fifty grams of the calcined alumina were suspended as a dilute slurry is deionized water and 50 cc. of a solution comprising 0.15 g. Pt (as PtCl were slowly added to the slurry. The excess liquid was decanted and the impregnated alumina was dried and calcined for 4 hours at 1000 F.

EXAMPLE 2 One part by Weight of the catalyst of Example 1 was mixed with 9 parts by weight of alumina gel particles prepared as per Example 1 and which were calcined at 1500 F. for 16 hours. This catalyst is designated as catalyst A. Another part by weight of the catalyst of Example 1 was heated for 24 hours at 1200 F. and mixed with 9 parts by weight of the 1500 F. heat treated alumina gel. This catalyst is designated catalyst B.

EXAMPLE 3 A sample of the catalyst prepared in Example 1 was impregnated with a solution of cerium nitrate in sufficient amount to provide 0.5 wt. percent Ce O in this catalyst. One part of this catalyst was heated for 16 hours at 1000 F. and another part was heated for 24 hours at 1200 F. Each of these heat treated catalysts were mixed with nine times as much (by weight) of alumina gel particles heated to 1500 F. for 16 hours as per Example 2 to form catalysts designated as catalysts C and D, respectively.

EXAMPLE 4 The procedure of Example 3 was repeated in all respects except that the amount of solution added was sutficient to provide 5.0 wt. percent Ce O on the catalyst concentrate. The dilute catalysts produced containing 0.03% Pt and 0.5% Ce O are designated as catalysts E and F, respectively.

EXAMPLE 5 Each of the above catalysts was used to hydroform a heavy virgin naphtha at 200 p.s.i.g., 910 F. sand bath temperature with 2000 cu.ft./b. of dry hydrogen in a four-hour period. Catalyst A was considered the standard and is rated at 100% activity. The relative activity of the other catalysts is set out in Table I.

It can be readily seen that catalysts D and F containing ceria as a stabilizer withstood the efiects of pro- 4 longed heating to 1200 F. much better than catalyst B which did not contain ceria.

EXAMPLE 6 Additional catalysts were prepared similarly to Example 1 but the amount of platinum was one tenth that used in Example 1 so that the catalyst contained only 0.03 wt. percent of platinum uniformly impregnated upon the alumina which had been previously calcined at 1500 F. for 16 hours. Samples of this catalyst were impregnated with 0.1% C6203 and 0.5% Ce O One sample of each of these catalysts was calcined for 4 hours at 1000 F. and one sample of each was calcined for 24 hours at 1200 F. Each of these catalysts was then tested as in Example 5. The activities of the several catalysts are all compared with the activity of catalyst A above as the standard. The results are summarized in Table II.

Table II Heat Deactivation (24 Hrs. at 1,200 F.) percent of Activity of Catalyst A Fresh Astlvity (Heated 4 Hrs. at 100 F.) percent of Activity of Catalyst A Percent Activity Loss Upon Heating Stabilizer These data clearly show that small amounts of ceria are highly effective in stabilizing platinum-alumina catalysts.

The foregoing description contains a limited number of embodiments of the present invention. It will be understood that numerous variations are possible without departing from the scope of this invention as defined by the following claims.

What is claimed is:

1. A reforming catalyst composition consisting essentially of from about 0.01 to 5 .0 wt. percent of a platinum group metal in combination with from 0.05 to 5.0 Wt. percent of ceria as the catalytic metal components supported upon an adsorptive alumina-containing carrier.

2. A reforming catalyst composition consisting essentially of from 0.01 to 1.0 wt. percent platinum in combination with from 0.05 to 5% ceria as the catalytic metal components supported upon an adsorptive alumina-containing carrier.

3. A reforming catalyst composition consisting essentially of about 0.2 to 1.0 wt. percent platinum and 0.5 to 5.0 wt. percent ceria as the catalytic metal components supported upon an adsorptive alumina carrier in finely divided form intimately mixed with several times the amount of finely unplatinized alumina.

'4. A method of reforming hydrocarbon fractions boiling in the naphtha boiling range which comprises contacting naphtha vapors in admixture with hydrogen at temperatures of from 800 to 1000" F. and pressures of from about to 1000 p.s.i.g. with a catalyst consisting essentially of from about 0.01 to 5.0 wt. percent of a platinum group metal in combination with from 0.05 to 5.0 wt. percent of ceria as the catalytic metal components supported upon an adsorptive alumina-containing carrier.

5. A method of reforming hydrocarbon fractions boiling in the naphtha boiling range which comprises contacting naphtha vapors in admixture with hydrogen at temperatures of from 800 to 1000 F. and pressures of from about 100 to 1000 p.s.i.g. with a catalyst consisting essentially of from 0.01 to 1.0 wt. percent platinum in combination with from 0.05 to 5% ceria as the catalytic metal components supported upon an adsorptive aluminacontaining carrier.

6. A method of reforming hydrocarbon fractions boiling in the naphtha boiling range which comprises contacting naphtha vapors in admixture with hydrogen at temperatures of from 800 to 1000 F. and pressures of 5 6 from about 100 to 1000 p.s.i.g. with a catalyst consisting References Cited in the file of this patent essentially of about 0.2 to 1.0 wt. percent platinum and UNITED STATES PATENTS 0.5 to 5.0 wt. percent ceri'a as the catalytic metal comv A 8 1952 ponents supported upon an adsorptive alumina carrier fifg zg -gg-gzi 1957 1 m finely dlvlded form mtlmate y mixed wlth several tunes 5 2,814,599 Lefrancois et a1 Nov 1957 the amount of finely unplatinized alumina. 

4. A METHOD OF REFORMING HYDROCARBON FRACTIONS BOILING IN THE NAPHTHA BOILING RANGE WHICH COMPRISES CONTACTING NAPHTHA VAPORS IN ADMIXTURE WITH HYDROGEN AT TEMPERATURES OF FROM 800 TO 1000*F. AND PRESSURES OF FROM ABOUT 100 TO 1000 P.S.I.G. WITH A CATALYST CONSISTING ESSENTIALLY OF FROM ABOUT 0.01 TO 5.0 WT. PERCENT OF A PLATINUM GROUP METAL IN COMBINATION WITH FROM 0.05 TO 5.0 WT. PERCENT OF CERIA AS THE CATALYTIC METAL COMPONENTS SUPPORTED UPON AN ADSORPTIVE ALUMINA-CONTAINING CARRIER. 